Gut feel is that 3,000 paid subscribers expect something significant - and unless you can automate this / hand it off to someone else - then it's not REALLY passive income yet - and can't easily be sold as a turn key business.
So a couple of questions arise ...
1/ If you are making $500K a year as your own boss in betting - why would you want to work for someone else for $100K or so?
You think bookmaking is that interesting that you'd lose $300-400K per year to do? Really?
My experience is having been your own boss ruins you as an employee ...
2/ What would be involved in automating / training others to run the existing sites so that it's passive income ?
If you can turn your existing sites into passive income then you could either
a/ Show that there is no conflict with your bookmaker / as you are not running the site only an owner ... or ...
b/ Demonstrate to a potential purchaser that the site is a turn key "cash machine" - not requiring time-in - so worth more ...
Business sales work best / get the best results when there is NOT a key person issue ...